The present invention relates to ignition systems for spark-ignition engines, and more particularly the invention relates to an ignition system capable of causing the spark plugs to discharge continuously.
The ignition system of a conventional spark-ignition engine comprises an ignition coil, a circuit breaker, etc., and it is so designed that the primary current flowing in the primary winding of the ignition coil is interrupted by the circuit breaker to generate a high voltage instantaneously in the secondary winding of the ignition coil and the high voltage is applied to the proper spark plug, thus instantaneously causing a capacitance discharge and thereby producing a single spark to ignite the mixture in the cylinder.
In recent years, to meet the restrictions on exhaust emissions and requirement for improved fuel consumption, engines have come into use in which leaner mixtures are used or a large quantity of exhaust gas recirculation (EGR) is used. However, the use of the previously mentioned known ignition system in these engines tended, due to the discharge period of the spark plugs being instantaneous, to cause misfiring due to the insufficient ignition energy and hence unsatisfactory ignition of the mixture and also to cause uneven combustions due to the unstable combustion.